Cervical Ripening, the dilation and effacement of the cervix is the most reliable indictor for predicting labor. In rodents, inhibitors of nitric oxide synthase (NOS) reduce cervical extensibility and prolong the duration of labor, suggesting that NOS may be a new therapeutic target for the treatment of premature labor. These data support a role for nitric oxide in cervical ripening but provide no information of the relative importance of the specific roles of the different nitric oxide synthase isoforms and the mechanism(s) by which nitric oxide affects cervical remodeling. The goal of this project is to study the role of nitric oxide in the activation of cervical collagenase and cervical ripening. We will initially examine the influence of nitric oxide on cervical collagenase activity during normal and induced labor in wildtype and iNOS-deficient mice. Mice provide a good model to study the role of nitric oxide in the cervix during labor because; 1) it is possible to induce labor in mice and 2) mice containing genetic deletions of NOS isoforms are available. Using information gained from the mouse studies, we will then conduct targeted experiments to examine the expression and activity of NOS in the human cervix during preterm and term labor. We hypothesize that the stimulation of inducible NOS (iNOS), which generates NO within the cervical stroma, results in the activation of procollagenase and leads to effacement and dilation, i.e. labor. Integral to this hypothesis is our prediction that a lack of iNOS would result in a decrease in collagenase activity and a delay in cervical remodeling and labor. Furthermore, we propose that inappropriate or precocious induction of INOS results in premature labor. Taken together, we would expect that iNOS levels and collagenase activity will be increased in cervices from women in both preterm and term labor in comparison to non-laboring pregnant women at term. The proposed studies will demonstrate the influence of NO, specifically synthesized by iNOS in the biochemical events resulting in cervical dilation, namely activation of collagenase. This information will further our basic understanding of the regulation of collagenase activity and are critical for development of future therapies for the prevention of preterm labor.